Multiple projects are underway to investigate the molecular mechanisms of cancer progression, with research emphasis on women's cancers. the role of the nm23 family of genes in the regulation of tumor metastasis was investigated. Reduced expression of nm23 protein levels in highly metastatic breast carcinomas was observed in two immunohistochemistry studies, and somatic allelic deletion of nm23-H1 was found to contribute to its reduced protein expression. Transfection of the human nm23-H1 cDNA into the metastatic human breast carcinoma cell line MDA-MB-435 is near completion. the nm23-H1 transfectants exhibited reduced activity upon growth in vitro, colonization in soft agar, responsiveness to TGF-B in colonization, and migration to serum, PDGF, and IGF in chemotaxis assays, as compared to control transfectants. Upon injection into the mammary fat pad, all lines formed primary mammary tumors, but the nm23-H1 transfectants produced metastases to the draining lymph node and/or lungs in significantly fewer mice. The data indicate that expression of the human nm23-H1 cDNA can suppress the malignant progression of this human breast carcinoma cell line. Transfection experiments using a human ovarian carcinoma cell line are underway. For both the murine K-1735 TK melanoma and human MDA-MB-435 breast carcinoma cell lines, nm23-H1 transfectants were more sensitive to inhibition of in vitro growth by the chemotherapeutic drug cisplatin than control transfectants. In the murine melanomas, nm23 transfectants also exhibited reduced levels of a protein thought to be part of the DNA repair complex, XPE-BF. The data suggest an unexpected association between suppressor gene expression and sensitivity to DNA damaging agents. Additional research has investigated the expression of the extracellular matrix protein thrombospondin (TSP) in cancer progression. Highly tumorigenic and/or metastatic cell lines from murine melanomas, human lung carcinomas and human breast carcinomas expressed quantitatively reduced TSP, as compared to less aggressive controls. The TSP cDNA has been subcloned into an expression construct, in anticipation of transfection experiments in human breast carcinoma construct, in anticipation of transfection experiments in human breast carcinoma cell lines. Molecular investigations are underway to evaluate the growth factor receptor and cyclin expression of premalignant lesions of the human breast.